Domestic security was radically and permanently changed by recent terrorist attacks. With these has come the sobering recognition that we are not adequately equipped to handle the detonation of a radiological dispersal device (RDD or so-called dirty bomb) or improvised nuclear device (IND). The development of rapid, minimally invasive biodosimetry that is field-deployable and reliable enough to guide decisions for the health care of populations exposed to multiple types of ionizing radiation under various conditions is a high priority. Our project addresses this priority and uses the powerful global profiling capabilities of metabolomics, a biomarker discovery platform uniquely suited for the analysis of biofluids such as blood and urine that require minimally- or non-invasive procedures to acquire. We have used metabolomics to define a urinary radiation response in mice and rats and are using these findings to guide discovery in humans. We propose to expand our research into more real-world scenarios such as (1) low dose-rate exposures, (2) partial body exposures resulting from shielding of certain organs and tissues, (3) exposures to radioisotopes following an IND or RDD, and (4) mixed exposures to neutrons and low linear energy transfer (LET) radiation typical of an IND. We are also focusing attention on the development of prognostic biomarkers to predict individual outcomes from near lethal exposures as well as the mechanisms involved in biomarker responses. Our studies will be conducted using several inbred strains of mice as well as three genetically modified mouse strains, all of which have varying sensitivities to ionizing radiation. For comparison, human peripheral white blood cell samples will also be analyzed after ex vivo irradiation. Our approach is to harness the exquisite resolution and accurate mass measurement capabilities of the Ultra-Performance Liquid Chromatography-time-of-flight mass spectrometry metabolomics platform that has proven enormously useful to date. Our metabolomics analyses will be run in parallel with transcriptomics analyses (Project 2) and cellular endpoints (Project 1), sharing many of the same samples. Our goals are to define a strategy for minimally invasive biodosimetry for relevant real-world radiation exposures and to find biomarkers by which the most severe radiation-related injuries may be identified as early as possible.